With development of the computer technology and the Internet technology, the Internet plays an important role in daily life, study, and work of people. Users are used to obtain information and share information through the Internet. For example, many websites provide ask and answer service. In another word, the websites receive questions from the user, display the questions, and receive answers to the question from other users. For example, some websites may specially supply ask and answer service, some websites maybe comprehensive or professional forums, and some websites maybe company websites which the users an exchange using experience of the products of the company.